There has conventionally been known an air conditioner comprising a refrigerant circuit and a refrigerant heating device for heating a refrigerant with warm water from a boiler (see, for example, Japanese Examined Patent Publication No. SHO 55-9618).
Specifically, the refrigerant circuit is composed of a compressor, an outdoor heat exchanger, an expansion mechanism, and an indoor heat exchanger which are connected to each other with piping. The refrigerant circuit has the refrigerant circulating through the inside thereof and a four-way switch valve such that the direction of circulation of the refrigerant is reversible. The air conditioner performs a cooling operation using a refrigeration cycle operation and a heating operation using a heat pump cycle operation. The air conditioner also performs a heating operation by supplying the refrigerant heated by the refrigerant heating device to the indoor heat exchanger. In short, the air conditioner performs both of the heating operation using the heat pump cycle operation and the heating operation using the refrigerant heating device.
On the other hand, the refrigerant heating device heats the refrigerant with warm water from a boiler. Specifically, the refrigerant heating device introduces the warm water generated by the boiler into a warm water tank and causes a heat exchange between the warm water in the warm water tank and the refrigerant. In short, the refrigerant heating device heats the refrigerant by using the sensible heat change of the warm water.
The air conditioner switches between the refrigeration cycle operation and the heat pump cycle operation. The outdoor heat exchanger of the refrigerant circuit functions as a condenser during the refrigeration cycle operation, while functioning as an evaporator during the heat pump cycle operation. Therefore, the specifications of the outdoor heat exchanger should be determined such that the outdoor heat exchanger exerts sufficient abilities as the condenser during the cooling operation and as the evaporator during the heating operation.
However, the optimum specifications for a condenser are different from the optimum specifications for an evaporator. Consequently, such a problem has been encountered that the outdoor heat exchanger optimized as an evaporator has an excessive ability as a condenser. Briefly, the specifications of the outdoor heat exchanger cannot be optimized as both the condenser and the evaporator. The problem leads to another problem that the operating conditions cannot be optimized during both the refrigeration cycle operation and the heat pump cycle operation, resulting in a reduction in energy efficiency.
The present invention has been achieved in view of the foregoing. It is therefore an object of the present invention to improve energy efficiency in an air conditioner comprising a refrigerant circuit.